The trade was not about him as the centerpiece on the return, in fact, he's the last guy on the list- in terms of value.
He was included to offset the financial cost to the other Phillies. The trade was about getting a young catcher, who is better than anyone in our current system, getting a RH'd hitting OF'er who may be better than Duran and a very nice pitching prospects- all while saving money that might allow us to sign a better FA.
Segura also fills a stop-gap role at SS or 2B.